JP7843894B2 - Preform for double-walled container molding - Google Patents

Description

This invention relates to a preform for double-walled container molding.

A preform for forming a double-walled container comprising an inner container that deforms in volume as the contents it contains decrease, and an outer container that houses the inner container and has an air intake hole formed between it and the inner container to introduce outside air as the contents decrease, comprises a bottomed cylindrical inner preform for forming the inner container and a bottomed cylindrical outer preform for forming the outer container.
As a preform for this type of double-walled container molding, a configuration is known in which an inner preform is fitted inside an outer preform, and a release agent layer is provided between the inner circumferential surface of the outer preform and the outer circumferential surface of the inner preform, as shown in Patent Document 1 below.
In a double-walled container formed with this preform, as the contents decrease, outside air is introduced between the inner and outer containers through the outside air intake holes, making it easier to separate the outer surface of the inner container from the inner surface of the outer container.

Japanese Patent Publication No. 2010-82916

However, the conventional double-walled container molding preform had a release agent layer between the inner surface of the outer preform and the outer surface of the inner preform, which presented a manufacturing difficulty.

This invention has been made in view of the circumstances described above, and aims to provide a preform for molding double-walled containers that allows the outer surface of the inner container to be easily separated from the inner surface of the outer container as the contents decrease, even without providing a release agent layer.

The present invention employs the following means to solve the above problems. That is, the present invention provides a preform for forming a double-walled container comprising: an inner container that deforms in volume as the contents it contains decrease; and an outer container in which the inner container is housed, and in which an air intake hole is formed to introduce outside air between the inner container and the outer container as the contents decrease, the preform comprises a bottomed cylindrical inner preform for forming the inner container and a bottomed cylindrical outer preform for forming the outer container, and the inner preform is placed inside the outer preform with the opening of the inner preform fitted into the opening of the outer preform A frame is inserted, and a vertical groove is formed on the inner circumferential surface of the mouth of the outer preform, extending downward from the upper opening edge of the outer preform. The outside air intake hole opens in the vertical groove. The mouth of the inner preform is provided with a flange portion that extends continuously along its entire circumferential length and abuts against the upper opening edge of the outer preform, closing the upper opening of the vertical groove. The outside air intake hole is separated downward from the upper opening edge of the outer preform, and the inner circumferential surface of the mouth of the outer preform and the outer circumferential surface of the mouth of the inner preform are in contact with each other over the entire area except for the vertical groove.

In this invention, a vertical groove is formed on the inner circumferential surface of the mouth of the outer preform, extending downward from the upper opening edge of the outer preform, and an outside air introduction hole is opened in the vertical groove. Therefore, even when the mouth of the inner preform is fitted into the mouth of the outer preform and relative movement between the outer and inner preforms is suppressed, when outside air is introduced between the inner container and the outer container through the outside air introduction hole, it passes through the vertical groove. This makes it easier to separate the outer circumferential surface of the inner container from the inner circumferential surface of the outer container as the contents decrease, even without providing a release agent layer.
Since the longitudinal grooves extend downward from the upper opening edge of the outer preform, the longitudinal grooves can be easily provided on the inner circumferential surface of the outer preform without complicating the structure of the molding die.
Since the inner preform is provided with a flange portion that extends continuously along its entire circumferential length and abuts against the upper opening edge of the outer preform, relative movement between the outer and inner preforms can be reliably suppressed.
Since the flange portion closes the upper end opening of the vertical groove, as the contents decrease, the portion in which outside air enters between the inner container and the outer container can be limited to the outside air intake hole. This makes it easier to maintain the momentum of the outside air when it enters between the inner and outer containers, making it easier to reliably separate the outer surface of the inner container from the inner surface of the outer container, and also makes it easier to reduce the size of the inner container as intended, thereby minimizing the amount of remaining contents.

The inner and outer circumferential surfaces of the opening of the inner preform may extend along the central axis in a longitudinal cross-sectional view along the central axis of the inner preform.

In this case, since the inner and outer circumferential surfaces at the opening of the inner preform extend along the central axis in a longitudinal cross-sectional view along the central axis of the inner preform, relative movement between the outer and inner preforms can be reliably suppressed.

The outer circumferential surface of the opening of the inner preform may be provided with a projection that extends radially outward, continuously along its entire circumferential length, and presses against the inner circumferential surface of the opening of the outer preform.

In this case, since the outer circumferential surface of the opening of the inner preform is provided with a protrusion that presses against the inner circumferential surface of the opening of the outer preform, relative movement between the outer and inner preforms can be reliably suppressed.

A diffusion gap extending continuously along the entire length in the circumferential direction may be provided between the connection portion between the outer circumferential surface of the inner preform and the lower surface of the flange portion, and the connection portion between the inner circumferential surface of the outer preform and the upper end opening edge.

In this case, a diffusion gap is provided between the connection point between the lower surface of the flange on the outer circumferential surface of the inner preform and the connection point between the inner circumferential surface and the upper opening edge of the outer preform. Therefore, as the contents decrease, the outside air introduced between the inner and outer containers through the outside air intake holes can circulate through the diffusion gap, making it easier to distribute the air throughout the entire circumferential length of the mouth of the double-walled container. This facilitates the reduction and deformation of the inner container to the desired shape.

According to this invention, even without providing a release agent layer, the outer surface of the inner container can be easily separated from the inner surface of the outer container as the contents decrease.

This is a top view of a preform for double-walled container molding, as shown in one embodiment. This is a semi-longitudinal cross-sectional view including the view taken along arrow II according to the first embodiment of Figure 1. This is a cross-sectional view taken along the line III in Figure 1, according to the first embodiment. This is a cross-sectional view taken along the line IV of the first embodiment shown in Figure 1. This is a cross-sectional view taken along the line III of the second embodiment in Figure 1. This is a cross-sectional view taken along the line IV of the second embodiment shown in Figure 1.

The preform for molding a double-walled container according to the first embodiment will be described below with reference to the drawings.
The double-walled container molding preform 1 is used to mold a double-walled container X, as shown in Figures 1 to 4, which comprises an inner container X1 that deforms in volume as the contents it contains decrease, and an outer container X2 in which the inner container X1 is housed, and which has an air intake hole 13 formed between it and the inner container X1 to introduce outside air as the contents decrease.
The double-walled container X is formed by blow molding a preform 1 for double-walled container molding. In the double-walled container X, the inner container X1 is highly flexible and is spaced apart on the inner surface of the outer container X2.

The double-walled container molding preform 1 comprises a bottomed cylindrical inner preform 11 for molding the inner container X1 and a bottomed cylindrical outer preform 12 for molding the outer container X2. In Figure 1, the inner preform 11 is hatched.
As shown in Figure 2, the opening 21 of the inner preform 11 (hereinafter referred to as the inner opening) is inserted into the opening 22 of the outer preform 12 (hereinafter referred to as the outer opening), and the bottom 23 of the inner preform 11 (hereinafter referred to as the inner bottom) is inserted into the bottom 24 of the outer preform 12 (hereinafter referred to as the outer bottom).

The inner preform 11 and the outer preform 12 are arranged coaxially with the common axis.
Hereinafter, this common axis will be referred to as the central axis O, the inner opening 21 side and the outer opening 22 side along the central axis O will be referred to as the upper side, and the inner bottom 23 side and the outer bottom 24 side along the central axis O will be referred to as the lower side. When viewed from above or below, the direction intersecting the central axis O will be referred to as the radial direction, and the direction revolving around the central axis O will be referred to as the circumferential direction.

The inner preform 11 and outer preform 12 are made of synthetic resin materials, and may be made of the same material or different materials. Examples of synthetic resin materials include PET (polyethylene terephthalate), PP (polypropylene), PE (polyethylene), nylon (polyamide), and EVOH (ethylene-vinyl alcohol copolymer).

As shown in Figure 4, the inner opening 21 is fitted inside the outer opening 22. The outer circumferential surface of the inner opening 21 abuts against the inner circumferential surface of the outer opening 22 along its entire length in the vertical direction.
As shown in Figure 2, a gap is provided between the outer circumferential surface of the inner preform 11 and the inner circumferential surface of the outer preform 12, in the portion located below the inner opening 21 and the outer opening 22, along the entire length in the vertical direction.

On the outer circumferential surface of the outer opening 22, a male threaded portion 22a to which a cap (not shown) is screwed, a sealing projection 22b to which the peripheral wall portion of the cap (not shown) is fitted, and a neck ring 22c are formed in this order from top to bottom.
The cap may also be fitted onto the outer opening 22 with an undercut.

The sealed projection 22b and the neck ring 22c project radially outward from the outer opening 22 and extend continuously along the entire circumferential length. The outer surface of the sealed projection 22b and the inner surface of the circumferential wall of the cap (not shown) are airtightly sealed. The outer diameter of the neck ring 22c is larger than the outer diameter of the sealed projection 22b. The neck ring 22c is located below the circumferential wall of the cap (not shown).

The aforementioned outside air intake hole 13 is formed in the outer opening portion 22. The outside air intake hole 13 is located radially on the outermost side of the sealed projection 22b and is positioned above the sealing surface that extends continuously along its entire circumferential length. The vertical positions of the outside air intake hole 13 and the lower part of the male threaded portion 22a are the same. Here, the male threaded portion 22a extends intermittently in the circumferential direction, and the outside air intake hole 13 is provided in the intermittent circumferential portion of this male threaded portion 22a.
A vertical groove 16 is formed on the inner circumferential surface of the outer opening portion 22, extending downward from the upper end opening edge 15 of the outer preform 12. An outside air intake hole 13 is opened in the vertical groove 16. The lower end of the vertical groove 16 is located below the neck ring 22c.

As shown in Figure 1, multiple air intake holes 13 and vertical grooves 16 are provided at equal intervals in the circumferential direction. In the illustrated example, four vertical grooves 16 are provided at 90° intervals around the central axis O when viewed from above and below. Of the four vertical grooves 16, one air intake hole 13 is opened in each of the two vertical grooves 16 that are radially opposite to each other. Note that air intake holes 13 may be opened in all vertical grooves 16, or multiple air intake holes 13 may be opened in a single vertical groove 16.

The inner opening 21 is provided with a flange portion 25 that extends continuously along its entire circumferential length and abuts against the upper end opening edge 15 of the outer preform 12. As shown in Figure 3, the flange portion 25 closes the upper end opening of the vertical groove 16.

As shown in Figure 4, the outer circumferential surface of the inner opening 21 is provided with a projection 26 that protrudes radially outward, extends continuously along its entire circumferential length, and is pressed against the inner circumferential surface of the outer opening 22. Multiple projections 26 are provided at intervals in the vertical direction. As shown in Figure 3, the projections 26 are located above the outside air intake hole 13 of the outer opening 22. Note that the projections 26 are not required.

The inner and outer circumferential surfaces of the inner opening 21 extend along the central axis O in a longitudinal cross-sectional view along the central axis O. Of the inner and outer circumferential surfaces of the inner opening 21, at least the inner circumferential surface extends parallel to the central axis O. In the illustrated example, the inner and outer circumferential surfaces of the inner opening 21 extend parallel to the central axis O. Here, "parallel" includes the draft angle from the molding die.

The inner opening portion 21 is the part of the inner preform 11 that includes the same position in the vertical direction relative to the lower surface of the neck ring 22c of the outer preform 12, and is located above it. In the double-walled container molding preform 1, the portion that includes the same position in the vertical direction relative to the lower surface of the neck ring 22c, and is located above it, is a portion whose shape does not change before and after blow molding.

On the outer circumferential surface of the inner preform 11, multiple ribs 11a are formed at circumferential intervals in the portion connected to the lower end of the inner opening 21, projecting radially outward and close to the inner circumferential surface of the outer preform 12. The ribs 11a maintain vertical communication between the outer circumferential surface of the inner container X1 and the inner circumferential surface of the outer container X2 in the double-walled container X.
The rib 11a may be a part whose shape does not change before and after blow molding, or it may be a part that abuts against the inner circumferential surface of the outer container X2 formed by the outer preform 12 after blow molding.

A diffusion gap A is provided between the connection portion between the outer circumferential surface of the inner preform 11 and the lower surface of the flange portion 25, and the connection portion between the inner circumferential surface of the outer preform 12 and the upper end opening edge 15, extending continuously along the entire length in the circumferential direction. The diffusion gap A opens into the vertical groove 16.
The connection portion between the outer circumferential surface of the inner preform 11 and the lower surface of the flange portion 25 is formed as a curved surface that is recessed radially inward. The connection portion between the inner circumferential surface of the outer preform 12 and the upper end opening edge 15 is formed as a curved surface that protrudes radially inward.

As described above, according to the double-walled container molding preform 1 of this embodiment, a vertical groove 16 is formed on the inner circumferential surface of the outer opening 22, extending downward from the upper opening edge 15 of the outer preform 12. Since an outside air inlet 13 is opened in the vertical groove 16, even when the inner opening 21 is fitted into the outer opening 22 and relative movement between the outer preform 12 and the inner preform 11 is suppressed, when outside air is introduced between the inner container X1 and the outer container X2 through the outside air inlet 13, it passes through the vertical groove 16. Therefore, even without providing a release agent layer, the outer circumferential surface of the inner container X1 can be easily separated from the inner circumferential surface of the outer container X2 as the contents decrease.

Since the vertical grooves 16 extend downward from the upper opening edge 15 of the outer preform 12, the vertical grooves 16 can be easily provided on the inner circumferential surface of the outer preform 12 without complicating the structure of the molding die.
Since the inner opening portion 21 is provided with a flange portion 25 that extends continuously along the entire length in the circumferential direction and abuts against the upper end opening edge 15 of the outer preform 12, relative movement between the outer preform 12 and the inner preform 11 can be reliably suppressed.

Since the flange portion 25 closes the upper end opening of the vertical groove 16, as the contents decrease, the portion of outside air entering between the inner container X1 and the outer container X2 can be limited to the outside air intake hole 13. This makes it easier to maintain the momentum of the outside air entering between the inner container X1 and the outer container X2, ensuring that the outer surface of the inner container X1 is reliably separated from the inner surface of the outer container X2. Furthermore, it becomes easier to achieve the desired shape of the reduced deformation of the inner container X1, thereby minimizing the amount of remaining contents.

Since the inner and outer circumferential surfaces of the inner opening 21 extend along the central axis O in a longitudinal cross-sectional view along the central axis O, relative movement between the outer preform 12 and the inner preform 11 can be reliably suppressed.

Since the outer circumferential surface of the inner opening 21 is provided with a protruding portion 26 that presses against the inner circumferential surface of the outer opening 22, relative movement between the outer preform 12 and the inner preform 11 can be reliably suppressed.

Since a diffusion gap A is provided between the connection portion between the lower surface of the flange portion 25 on the outer circumferential surface of the inner preform 11 and the connection portion between the inner circumferential surface of the outer preform 12 and the upper end opening edge 15, as the contents decrease, the outside air introduced between the inner container X1 and the outer container X2 through the outside air introduction hole 13 can be circulated through the diffusion gap A, making it easier to distribute the outside air over the entire circumferential length of the mouth of the double container X, and thus making it easier to achieve the desired shape when the inner container X1 shrinks and deforms.

Next, the double-walled container molding preform 2 according to the second embodiment will be described with reference to Figures 5 and 6.
In the second embodiment, the same reference numerals are used for parts that are the same as those in the first embodiment, and their descriptions are omitted. Only the differences will be described.

In this embodiment, the rib 11a is in contact with the inner circumferential surface of the outer preform 12. The upper end of the rib 11a and the lower end of the longitudinal groove 16 are at the same vertical position. The lower end of the rib 11a is located below the longitudinal groove 16.
In the double-walled container molding preform 2, the boundary between the portion whose shape does not change before and after blow molding and the portion that is stretched during blow molding is located at the contact portion of the rib 11a that is in contact with the inner circumferential surface of the outer preform 12.
In addition, in the double-walled container molding preform 2, the portion of the inner opening 21 and the portion of the rib 11a that is in the same vertical position as the contact portion may be designated as a portion whose shape does not change before and after blow molding, while the portion of the rib 11a located below the contact portion may be designated as a portion that is stretched during blow molding.

As described above, the double-walled container molding preform 2 according to this embodiment, similar to the double-walled container molding preform 1, makes it possible to easily separate the outer surface of the inner container X1 from the inner surface of the outer container X2 as the contents decrease, even without providing a release agent layer.

Furthermore, the technical scope of the present invention is not limited to the embodiments described above, and various modifications can be made without departing from the spirit of the invention.

A diffusion gap A does not need to be provided between the connection portion between the lower surface of the flange portion 25 on the outer circumferential surface of the inner preform 11 and the connection portion between the inner circumferential surface of the outer preform 12 and the upper end opening edge 15.

Furthermore, without departing from the spirit of the present invention, the components in the above embodiments may be replaced with well-known components as appropriate, and the above embodiments and modifications may be combined as appropriate.

1, 2 Preforms for double-walled container molding 11 Inner preform 12 Outer preform 13 Air intake hole 15 Upper opening edge 16 Vertical groove 21 Inner opening (opening of inner preform)
22. Outer opening (opening of the outer preform)
25 Flange section 26 Protruding section A Diffusion gap O Central axis X Double container X1 Inner container X2 Outer container

Claims (4)

The inner container deforms and decreases in volume as the contents it holds decrease,
A preform for forming a double container comprising: an inner container in which the inner container is housed, and an outer container having an air intake hole formed between it and the inner container for introducing outside air as the contents decrease,
It comprises a bottomed cylindrical inner preform for forming the inner container and a bottomed cylindrical outer preform for forming the outer container,
With the opening of the inner preform fitted into the opening of the outer preform, the inner preform is inserted into the outer preform.
A longitudinal groove is formed on the inner circumferential surface of the opening of the outer preform, extending downward from the upper opening edge of the outer preform.
The aforementioned vertical groove has an opening for the outside air intake,
The opening of the inner preform is provided with a flange portion that extends continuously along its entire circumferential length and abuts against the upper end opening edge of the outer preform, thereby closing the upper end opening of the vertical groove.
The aforementioned outside air intake hole is located away from the upper opening edge of the outer preform,
A preform for double-walled container molding, wherein the inner circumferential surface of the mouth of the outer preform and the outer circumferential surface of the mouth of the inner preform are in contact with each other over the entire area except for the longitudinal groove. The inner and outer circumferential surfaces of the inner preform at the mouth portion extend along the central axis in a longitudinal cross-sectional view along the central axis of the inner preform, as described in claim 1. The double-walled container molding preform according to claim 1 or 2, wherein the outer circumferential surface of the mouth of the inner preform is provided with a projection that protrudes radially outward, extends continuously along the entire length in the circumferential direction, and presses against the inner circumferential surface of the mouth of the outer preform. The connection portion between the outer circumferential surface of the inner preform and the lower surface of the flange portion,
The connection portion between the inner circumferential surface and the upper opening edge of the outer preform,
A preform for double-walled container molding according to any one of claims 1 to 3, wherein a diffusion gap is provided between them, extending continuously along the entire length in the circumferential direction.